With the development of communication and multimedia technologies, large-capacity transmission technologies are being applied to mobile communication systems. One of the core issues is an increase in radio capacity. The simplest scheme for increasing radio capacity is to allocate more frequency bands, but this is difficult to implement due to limited frequency resources. What is, therefore, required is a method for using limited frequency resources more efficiently. To this end, a method for increasing the frequency efficiency and a method for reducing the service cell size are considered. In particular, by reducing the service cell size, a better radio environment can be provided to a plurality of user terminals.
A femto cell, according to a method for reducing the service cell size, provides a service of a micro BS used in an indoor place such as home or office. A femto cell provides a wired/wireless integrated service at a low cost by means of mobile phones and the Internet. A macro BS serving a macro cell is installed by a mobile communication provider, whereas a micro BS (i.e., an SC BS) serving a femto cell is installed by a user. Thus, there may be a plurality of SC BSs that serve a femto cell within the macro cell of a macro BS. Also, the SC BSs may be installed or removed at the user's discretion.
Transmission of a preamble signal for frame synchronization is necessary for an operation of a BS. Thus, it is self-evident that the SC BSs can also transmit preamble signals. In this case, it is necessary to physically divide preamble signals transmitted by different BSs. Herein, preamble indexes are used to divide the preamble signals. The preamble index includes a segment IDentifier (ID) and an ID cell, which are parameters related to a preamble code, scrambling, and subchannelization. Thus, if two adjacent BSs use the same preamble index, a strong interference occurs between the preamble signals of the adjacent BSs. Therefore, the preamble indexes can be suitably allocated.
What is being considered is a broadband wireless communication system that uses SC BSs to increase radio capacity as described above. However, because the SC BSs are installed and removed at the user's discretion, the parameters for operating the SC BSs can be set adaptively according to the communication environments. In particular, a preamble index can be set as a basic parameter for operating the SC BS as a base station. What is, therefore, required is a scheme for suitably allocating the preamble indexes of the SC BSs in a broadband wireless communication system.